This project is a study of the role of somatic sensory inputs to the cerebral cortex in the control of motor behavior in primates. The first part of the project consists of a comparison of neural activity in the somatic sensory cortex (SI) and the precentral motor cortex (MI) with patterns of muscle activity during voluntary limb movements. The second part of the project is a detailed examination of the signals which the peripheral receptors are sending to the cortex during perturbation of voluntary movements. Such information should provide important clues concerning the role of peripheral inputs to MI in the initiation and control of movement.